This invention relates to half-cells using organic compounds as the depolarizer. More particularly it relates to cells using halide salts of N,N'-bis(substituted phenyl)-4,4'-dipyridyl as the organic depolarizer.
As cells using organic compounds as active materials, cells comprising cathode depolarizers of organic compounds shown below have been proposed, organic nitro compounds typified by m-dinitrobenzene, azodicarbonamides typified 1,1'-azobis(N-propylformamide) and charge transfer complexes from halogens and organic compounds typified by poly-2-vinyl quinoline, poly-2-vinyl pyridine and iodine.
In the above cells comprising organic depolarizers, electrolytes containing mainly liquid ammonia or organic solvents or solid electrolytes are used since these organic depolarizers are unstable or insoluble in aqueous media. For example, in the case of a cell containing m-dinitrobenzene it utilizes advantageously the feature that m-dinitrobenzene is soluble in liquid ammonia and is said to be excellent in low-temperature performance. A special pressure vessel is necessary for holding liquid ammonia, however, the weight efficiency of the cell is small and its use is restricted in respect of safety. A cell using a charge transfer complex obtained from poly-2-vinyl quinoline, poly-2-vinyl pyridine and iodine, or an ammonium organic polyiodide has less toxicity and corrosion properties with iodine which acts as a cathode depolarizer since iodine is fixed in the form of easy-to-handle solid organic compounds mentioned above. In these cells, however, the use of a solid electrolyte or an aprotic organic solvent as the liquid electrolyte lowers the specific conductivity of the electrolyte and increases the internal resistance of the cells, which is not good for the function of the cell. Moreover, the above iodine compounds are not completely stable, which affects the shelf-life of the cells adversely.
Recently rechargeable cells (secondary batteries) using a dipyridinium salt as the depolarizer for both cathode and anode have been proposed by Kondo et al in Japanese Patent Application Laid-open No. 77830/1976, in which the dipyridinium salt is represented as follows: ##STR1## where R.sub.1, R.sub.2, R.sub.3, R.sub.4 are H, alkyl, cycloalkyl, aryl, or alkaryl, which may be substituted; X.sup.- is Cl.sup.-, Br.sup.-, I.sup.-, PF.sub.6.sup.-, BF.sub.4.sup.-, or ClO.sub.4.sup.-. As a concrete example, however, only N,N'-bis-n-heptyl-4,4'-dipyridinium dibromide has been shown while the effect of the dipyridinium salts bearing aromatic rings such as dinitrophenyl or cyanophenyl has not yet been disclosed.